It's like the old story of a traveling man who stopped at a shop on the edge of town. He struck up a conversation with the owner and asked, "What kind of people live here?" The owner asked, "What type of people live where you hail from?"
"Thieves and conmen mostly," was the reply.
"That's what you'll find here, too," commented the shop owner.
Simply, no matter where you go, you will see and find both good and bad. It's rare I don't fish a water, especially popular waters, and see someone "stretching" the rules. This is true across the country.
Best you can do is either address the issue directly, dangerous, but often gets quick results in they move on, or call the authorities, which is my recommendation. Or simply ignore it and go about your business, but that, like complaining, isn't a solution in my opinion.